For some reason, people tend to describe foods that taste terrible in terms of things that no sane person has any right to know what it tastes like. The name comes from the episode of Friends where Rachel accidentally combines an English Trifle and a Shepherd's Pie, making the world's first (and hopefully last) Shepherd's Trifle. See it here. Meat, onions, whipped cream and jam? And just how would Ross know what feet taste like? A sister trope to Lethal Chef. Also, some people probably would know what feet taste like, such as Quentin Tarantino, or Joss Whedon.